The venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. Many hospital patients require a supplementary level of oxygen in the room air they are breathing, rather than pure or near pure oxygen and this can be delivered through a number of devices dependant on the diagnoses, clinical condition of a patient, level of blood oxygenation (hypoxemia), flow requirement and in some instances patient preference. There are also a number of devices available for oxygen delivery in a spontaneously breathing patient, some of the options being low flow nasal cannula, high flow nasal cannula, face mask, venturi mask, non-rebreather mask, oxygen tent, CPAP/BIPAP mask, etc. The venturi mask is especially desirable where highly controlled low concentration is required, especially in patients who are sensitive to high concentration oxygen and are at a risk of carbon dioxide retention when given high concentration oxygen (an example of such patient would be one with the diagnoses of COPD).
The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. Venturi devices often use flow rates between 2 and 12 LPM, with a concentration of oxygen delivered to the patient of between 24% and 50%. Venturi masks are considered high-flow oxygen therapy devices. This is because venturi masks are able to provide total inspiratory flow at a specified FiO2 (fraction of inspired oxygen) to a patient's therapy. The kits usually include multiple jets in order to set the desired FiO2 which are usually color coded. The color of the device reflects the delivered oxygen concentration, for example: blue=24%; yellow=28%; white=31%; green=35%; pink=40%; orange=50%. The color however varies with different brands and the user must check the instructions for use to determine the correct color for the desired FiO2. A venturi connector can be used and is connected to the patent through a face mask or the like and to a gas source (in this case oxygen) which delivers oxygen to the patient by means of the face mask. The venturi connector has air entrainment openings or ports that draw air into the connector for mixing with the gas (oxygen) that is flowing through the venturi connector to deliver a metered amount of a gas mixture to the patient.
Though venturi masks may accurately deliver a predetermined oxygen concentration to the trachea, generally up to 50%, there could be a greater level of inaccuracy in delivering higher concentration when a patient's flow requirement is high during respiratory distress and a high level of air entrainment happens through the secondary entrainment ports that are mostly a part of the interface mask device. There may be a reasonable level of predictability when considering primary air entrainment from the primary venturi entrainment ports but there is high level of unpredictability when considering the secondary entrainment from the interface mask device entrainment ports. Hence, a patient could be at a risk of developing hypoxemia due to inaccurately delivered low oxygen concentration than stated or predicted. The current venturi devices are therefore fraught with problems and need improvement and better accuracy or predictability.
There are other disadvantages with a venturi system, and that is that there are a large number of parts that are included in the venturi kit, especially multiple venturi connectors and therefore, the kit can be rather bulky and cumbersome. For example, if the oxygen concentration has to be varied, a completely new venturi connector having the proper jet (nozzle) is needed and thus, requires the previous nozzle to be removed and then the new nozzle is connected to the rest of the equipment. In addition, the flow of oxygen has to be adjusted for each venturi connector. This task requires time and moreover, is an interruption to the patient's treatment. In addition, most medical providers other than respiratory therapists are not easily familiar with the intricacies of venturi devices, they are not familiar with venturi principals, they require special training, and as such the devices currently being used are not user friendly. The parts of the kit that are not used, thus must be carefully stored and kept track of and could easily get misplaced which is not common in a hospital setting.
There is therefore a need for an improved venturi gas delivery system.